1. Field of the Invention
The present invention is a divisional of application Ser. No. 09/337,425, filed on Jun. 21, 1999, which relates to a thin film magnetic head in which a recording head (inductive magnetic head) and a reproducing head (magnetoresistive head) are combined, and more particularly, to a thin film magnetic head in which the tip and the vicinity thereof of an upper core layer can be formed in a predetermined shape, enabling the track to be narrowed, and to a method of fabricating the same.
2. Description of the Related Art
FIG. 11 is a longitudinal sectional view of a conventional thin film magnetic head.
The thin film magnetic head is provided on the trailing end of a slider of a floating type magnetic head which faces a recording medium such as a hard disk, and is a combined thin film magnetic head in which a magnetoresistive head for reproducing, using magnetoresistance, and an inductive magnetic head for recording, are laminated.
A lower shielding layer 1 is composed of a magnetic material such as an NiFe alloy (permalloy), and a magnetoresistive element layer 2 is formed on the lower shielding layer 1 with a first gap layer (not shown in the drawing) therebetween. An upper shielding layer 3, which is composed of a magnetic material such as an NiFe alloy, is formed on the magnetoresistive element layer 2. As described above, the thin film magnetic head shown in FIG. 11 is a combined thin film magnetic head in which a magnetoresistive head and an inductive magnetic head are laminated, and the upper shielding layer 3 also functions as a lower core layer of the inductive magnetic head. Hereinafter, the layer represented by numeral 3 is referred to as a lower core layer.
A gap layer 4 (second gap layer) composed of a nonmagnetic material such as aluminum oxide (Al2O3) or silicon dioxide (SiO2) is formed on the lower core layer 3. An insulating layer 5 (first insulating layer) composed of a resist or other organic material is formed on the gap layer 4.
A coil layer 6, composed of a conductive material having low electrical resistance, such as Cu, is spirally formed on the insulating layer 5. Although the coil layer 6 is formed so as to go around a base 8b of an upper core layer 8, which will be described later, only a portion of the coil layer 6 is shown in FIG. 11.
The coil layer 6 is covered by an insulating layer 7 (second insulating layer) composed of an organic material or the like, and the upper core layer 8 is formed on the insulating layer 7 by plating a magnetic material such as a permalloy. The tip 8a of the upper core layer 8 is joined to the lower core layer 3 with the gap layer 4 therebetween at the section facing a recording medium to form a magnetic gap having a gap length Gl. The base 8b of the upper core layer 8 is magnetically connected to the lower core layer 3 through a hole made in the gap layer 4.
In the inductive magnetic head for writing, when a recording current is applied to the coil layer 6, a recording magnetic field is induced in the lower core layer 3 and the upper core layer 8, and a magnetic signal is recorded onto a recording medium such as a hard disk by means of a leakage magnetic field from the magnetic gap between the lower core layer 3 and the tip 8a of the upper core layer 8.
In the thin film magnetic head shown in FIG. 11, the coil layer 6 has a double-layered structure. The double-layered structure is employed for the purposes of enhancing writing efficiency by shortening the magnetic path formed over the lower core layer 3 and the upper core layer 8, and reducing inductance.
FIG. 12 is a longitudinal sectional view which shows a step of fabricating the upper core layer 8 of the thin film magnetic head shown in FIG. 11.
The upper core layer 8 of the thin film magnetic head shown in FIG. 11 is formed by frame plating. As shown in FIG. 12, after the coil layer 6 is formed and is covered by the insulating layer 7, an underlying layer 9 composed of a magnetic material such as an NiFe alloy is formed from on the gap layer 4, which is exposed around the tip, to on the insulating layer 7.
Next, after a resist layer 10 is formed on the underlying layer 9, a pattern of the upper core layer 8 is formed on the resist layer 10 by exposure and development, and a magnetic material layer (upper core layer 8) is formed by plating on the section in which the resist 10 is removed and the underlying layer 9 is exposed. When the remaining resist layer 10 is removed, the upper core layer 8 is completed. In the final step, by removing the thin film laminate on the left side of the line Axe2x80x94A (shown by dotted lines in the drawing), the thin film magnetic head having the shape shown in FIG. 11 can be obtained.
However, in the structure of the conventional thin film magnetic head as shown in FIG. 11, when the upper core layer 8 is formed by frame plating, narrowing of the track cannot be realized.
As shown in FIG. 11, by forming the coil layer 6 having a double-layered structure, the total thickness of the insulating layers 5 and 7 which cover the coil layer 6 is increased, and in such a state, as shown in FIG. 12, when the resist layer 10 is formed from on the gap layer 4 around the tip in which the insulating layers 5 and 7 are not formed to on the insulating layer 7, the thickness tl of the resist layer 10 formed on the gap layer 4 is significantly increased. On the gap layer 4, as shown in FIG. 11, the tip 8a of the upper core layer 8 is formed. The tip 8a is narrowly shaped as shown in the plan view of FIG. 13, and the width of the tip 8a determines a track width Tw. In particular, as recording density is increased, the track width Tw must be further decreased, and the pattern of the resist layer 10 must be formed with particular precision when the tip 8a and its vicinity of the upper core layer 8 are formed.
However, as shown in FIG. 12, since the thickness tl of the resist layer 10 on the gap layer 4, in which the tip 8a of the upper core layer 8 is to be formed, is significantly increased, when the wavelength of a light source for exposure is decreased and the depth of focus is increased, resolution (resolving power) is degraded and the track width Tw having a predetermined size cannot be obtained; it is thus not possible to meet the need for narrowing of a gap. In order to improve resolution, a smaller depth of focus is better.
Another reason for not being able to realize narrowing of the track is that since the thickness tl of the resist layer 10 formed on the gap layer 4 differs greatly from that of the resist layer 10 formed on the insulating layer 7, irregular reflection may occur during exposure and development because of differences in focus.
FIG. 14 is a longitudinal sectional view of another conventional thin film magnetic head.
In FIG. 14, a lower shielding layer 11 is partially formed only around the tip, and a magnetoresistive element layer 12 is formed on the lower shielding layer 11. A lower core layer 13 (upper shielding layer) is formed from on the magnetoresistive element layer 12 and to in the rear of the lower shielding layer 11. A coil layer 14 is formed on the lower core layer 13, and an upper core layer 15 is formed so as to face the lower core layer 13 at the tip and to extend over an insulating layer 17 formed on the coil layer 14.
In the conventional example, the lower shielding layer 11 is partially formed only around the tip, and in the rear of the lower shielding layer 11, the lower core layer 13 is lowered to the same level as that of the lower shielding layer 11 through an inclined plane 13a. As shown in FIG. 14, the coil layer 14 is formed from on the inclined plane 13a to on the lower core layer 13 lying in the rear of the inclined plane 13a. Therefore, the insulating layer 17 is formed on the coil layer 14, being swollen from the surface S of the lower core layer 13 in the tip section by height t5, and the height t5 is smaller than the total thickness of the insulating layers 5 and 7 of the thin film magnetic head shown in FIG. 11. Accordingly, the thickness of a resist layer (not shown in the drawing; refer to numeral 10 in FIG. 12), which is formed on the lower core layer 13 around the tip, is not extremely increased, and in comparison with the thin film magnetic head shown in FIG. 11, a tip 15a of the upper core layer 15 can be easily formed in a predetermined shape.
In the thin film magnetic head shown In FIG. 14, however, the following problems may occur.
Generally, when a thin film magnetic head is formed, a plurality of thin film magnetic heads is simultaneously formed on a substrate 16 and by dividing into the individual thin film magnetic heads in the end, the thin film magnetic head shown in FIG. 14 can be obtained. That is, first, a plurality of lower shielding layers 11 is formed on the substrate 16, and a magnetoresistive element layer 12 is formed on each lower shielding layer 11 with an insulating layer (not shown in the drawing) therebetween. Next, a resist layer is applied onto a plurality of magnetoresistive element layers 12, and a track width Tw of the magnetoresistive element layer 12 is determined by exposure and development.
However, as described above, a plurality of magnetoresistive element layers 12 is placed on the substrate 16, and when the resist layer is, for example, spin-coated thereon, the surface onto which the resist layer is applied is not planar because the lower shielding layers 11 are selectively formed and there are steps between the lower shielding layers 11 and the substrate 16. Therefore, the resist layer is not formed at a uniform thickness, and a plurality of magnetoresistive element layers 12 formed on the substrate 16 cannot have a predetermined track width Tw.
In the thin film magnetic head shown in FIG. 14, the lower core layer 13 is provided with the inclined plane 13a, and the coil layer 14 is formed from on the inclined plane 13a to on the rear of the lower core layer 13. Since there is a difference in level on the inclined plane 13a on which the coil layer 14 is to be formed, the coil layer 14 is formed on the inclined plane 13a at a position that is raised upward in the drawing, and thus the thickness of the insulating layer 17 for covering the coil layer 14 must be increased. If the thickness of the insulating layer 17 is increased, it is difficult to form the tip 15a of the upper core layer 15 at a predetermined shape by frame plating, and narrowing of the track cannot be realized.
The present invention overcomes the difficulties noted above with respect to the related art. It is an object of the present invention to provide a thin film magnetic head, in which narrowing of the track is enabled by reducing the swelling of an insulating layer formed on a coil layer so that a tip of an upper core layer is formed in a predetermined shape and a magnetoresistive element layer is formed at a predetermined track width Tw, and to provide a method of fabricating the same.
In one aspect, a thin film magnetic head, in accordance with the present invention, includes a lower shielding layer composed of a magnetic material; a nonmagnetic MR gap layer formed on the lower shielding layer; a magnetoresistive element layer lying in the MR gap layer and facing a recording medium; a lower core layer composed of a magnetic material formed on the MR gap layer; an upper core layer composed of a magnetic material being opposed to the lower core layer with a nonmagnetic gap layer therebetween at the surface facing the recording medium; and a coil layer for inducing a recording magnetic field to the lower core layer and the upper core layer. The lower core layer extends from the position facing the recording medium to the rear of the magnetoresistive element layer, bends toward the lower shielding layer in the rear, and comes into magnetic contact with the lower shielding layer. The coil layer lies in the rear of a step of the back end of the lower core layer and lies magnetically between the lower shielding layer and the upper core layer. A magnetic path induced by the coil layer is formed over the lower shielding layer, the lower core layer, and the upper core layer.
In another aspect, a thin film magnetic head, in accordance with the present invention, includes a lower shielding layer composed of a magnetic material; a first magnetic material layer formed in the rear of the lower shielding layer and being magnetically separated from the lower shielding layer; a nonmagnetic MR gap layer formed on the lower shielding layer; a magnetoresistive element layer lying in the MR gap layer and facing a recording medium; a lower core layer composed of a magnetic material formed on the MR gap layer; an upper core layer composed of a magnetic material being opposed to the lower core layer with a nonmagnetic gap layer therebetween at the surface facing the recording medium; and a coil layer for inducing a recording magnetic field to the lower core layer and the upper core layer. The lower core layer extends from the position facing the recording medium to the rear of the magnetoresistive element layer, bends toward the first magnetic material layer in the rear, and comes into magnetic contact with the first magnetic material layer. The coil layer lies in the rear of a step of the back end of the lower core layer and lies magnetically between the first magnetic material layer and the upper core layer. A magnetic path induced by the coil layer is formed over the first magnetic material layer, the lower core layer, and the upper core layer.
In the above thin film magnetic head, preferably, a nonmagnetic material layer is provided between the lower shielding layer and the first magnetic material layer, and the lower shielding layer, the first magnetic material layer, and the nonmagnetic material layer have the same thickness.
In the present invention, preferably, the lower shielding layer and the first magnetic material layer are composed of different magnetic materials, and for example, the first magnetic material layer is composed of a magnetic material having higher saturation flux density and/or higher resistivity than that of the lower shielding layer.
A second magnetic material layer may be formed on the lower shielding layer or the first magnetic material layer in the rear of the coil layer, and the upper core layer is brought into contact with the second magnetic material layer.
Preferably, the second magnetic material layer is composed of a magnetic material having higher saturation flux density and/or higher resistivity than that of the lower shielding layer.
In the present invention, the coil layer may be formed in a double-layered structure, and at least the lower coil layer is placed in the rear of a step of the back end of the lower core layer, thus enabling a larger recording magnetic field and a thinner head.
In still another aspect, a method of fabricating a thin film magnetic head, in accordance with the present invention, includes the steps of: forming a lower shielding layer composed of a magnetic material by frame plating; forming a first gap layer on the lower shielding layer and forming a magnetoresistive element layer thereon for facing a recording medium; making a hole in the first gap layer in the rear of the magnetoresistive element layer so as to reach the lower shielding layer and forming a lower core layer extending from the hole to on the magnetoresistive element layer by frame plating; forming a second gap layer composed of a nonmagnetic material from on the lower core layer to on the first gap layer formed in the rear of the lower care layer; forming a first insulating layer on the first gap layer in the rear of the lower core layer with the second gap layer therebetween and forming a coil layer on the first insulating layer; and forming a second insulating layer on the coil layer, and then forming an upper core layer from on the gap layer formed on the lower core layer to on the second insulating layer by frame plating.
Alternatively, a method of fabricating a thin film magnetic head, in accordance with the present invention, includes the steps of: forming a lower shielding layer composed of a magnetic material and a first magnetic material layer lying in the rear of the lower shielding layer by frame plating; forming a first gap layer on the lower shielding layer and the first magnetic material layer, and forming a magnetoresistive element layer thereon for facing a recording medium; making a hole in the first gap layer in the rear of the magnetoresistive element layer so as to reach the first magnetic material layer and forming a lower core layer extending from the hole to on the magnetoresistive element layer by frame plating; forming a second gap layer composed of a nonmagnetic material from on the lower core layer to on the first gap layer formed in the rear of the lower care layer; forming a first insulating layer on the first gap layer in the rear of the lower core layer with the second gap layer therebetween and forming a coil layer on the first insulating layer; and forming a second insulating layer on the coil layer, and then forming an upper core layer from on the gap layer formed on the lower core layer to on the second insulating layer by frame plating.
The method may include the steps of forming a nonmagnetic material layer between the lower shielding layer composed of a magnetic material and the first magnetic material layer in the rear of the lower shielding layer, and grinding the lower shielding layer, the first magnetic material layer, and the nonmagnetic material layer down to the same thickness.
Before the second gap layer is formed, a hole may be made in the first gap layer on the lower shielding layer or the first magnetic material layer in the rear of the section in which the coil layer is formed, a second magnetic material layer may be formed by frame plating, and the upper core layer may be formed so as to be brought into contact with the second magnetic material layer through the hole.
Furthermore, the coil layer may be formed in a double-layered structure, and at least the lower coil layer may be formed in the rear of the lower core layer.
Preferably, the first magnetic material layer and the second magnetic material layer are composed of a magnetic material having higher saturation flux density and/or higher resistivity than that of the lower shielding layer.
In the present invention, a lower core layer (upper shielding layer) is partially formed only around the tip of a thin film magnetic head, the lower core layer bends perpendicularly on the back of a magnetoresistive element layer to form a step, and the lower core layer is brought into contact with a lower shielding layer or a first magnetic material layer. A coil layer is formed in the rear of the lower core layer that is bent perpendicularly, and thus the swelling of an insulating layer for covering the coil layer can be decreased in relation to the surface of the lower core layer exposed around the tip. Therefore, in the present invention, a resist layer used when an upper core layer is formed can be formed thinly without a large difference in the film thickness from on the lower core layer exposed around the tip to on the insulating layer covering the coil layer. The tip of the upper core layer formed on the lower core layer exposed around the tip is an important section for determining a track width Tw, and in the present invention, the tip of the upper core layer can be properly formed in a predetermined shape, thus meeting the demand to narrow the track.
Next, differences between the structure of a thin film magnetic head in the present invention and that of the conventional thin film magnetic head shown in FIG. 14 will be described.
In the present invention, in the manner same as that in the thin film magnetic head shown in FIG. 14, a lower shielding layer may be formed only around the tip, and as a specific structure, a thin film magnetic head shown in FIG. 2 may be presented.
A difference between the present invention and the conventional thin film magnetic head shown in FIG. 14 is that in the present invention, as shown in FIG. 2, in the rear of a lower shielding layer 30, a first magnetic material layer 31 having the same height as that of the lower shielding layer 30 is formed with a predetermined distance L2 therebetween, and in contrast, in the conventional thin film magnetic head shown in FIG. 14, in the rear of the lower shielding layer 11, the lower core layer 13 is formed by lowering its position through the inclined plane 13a. 
In the present invention, after the lower shielding layer 30 and the first magnetic material layer 31 are formed, a nonmagnetic material layer 32 composed of Al2O3 or the like is formed between the lower shielding layer 30 and the first magnetic material layer 31, and surfaces of the lower shielding layer 30, the first magnetic material layer 32, and the nonmagnetic material layer 32 are planarized. A magnetoresistive element layer 22 formed on the lower shielding layer 30 is formed into a predetermined shape by a resist layer (not shown in the drawing). Since the resist layer is applied onto the planarized lower shielding layer 30, first magnetic material layer 31, and nonmagnetic material layer 32, the resist layer can be formed at a uniform thickness, and therefore, the magnetoresistive element layer 22 can be formed at a predetermined track width Tw by the resist layer.
In contrast, in the conventional thin film magnetic head shown in FIG. 14, only the lower shielding layer 11 is partially formed on the substrate, and when a resist layer (not shown in the drawing) for forming the magnetoresistive element layer 12 into a predetermined shape is applied onto the lower shielding layer 11, because of a difference in level between the substrate 16 and the lower shielding layer 11, the resist layer cannot be formed at a uniform thickness, resulting in strain in the magnetoresistive element layer 12, and thus the track width Tw of the magnetoresistive element layer 12, which must be formed with particular precision, cannot be formed properly.
In the thin film magnetic head shown in FIG. 14, since the inclined plane 13a is provided in the lower core layer 13, a difference in level easily occurs in the section in which the coil layer 14 is formed in the rear of the lower core layer 13. In the present invention, as shown in FIG. 2, since the lower core layer 33 is formed perpendicularly from the first magnetic material layer 31, a coil layer 27 formed in the rear of the lower core layer 33 can be formed on a planarized first gap layer 23 with a second gap layer 25 and an insulating layer 26 therebetween, and thus, the formation of the coil layer 27 is facilitated and the swelling of an insulating layer 28 formed on the coil layer 27 can be reduced as much as possible.